As industry has continued to refine and improve production techniques and procedures, corresponding requirements have been levied for placing identifying, data related markings upon components of manufactured assemblies. With such marking, the history of a product may be traced throughout the stages of its manufacture and components of complex machinery such as automobiles and the like may be identified, for example, in the course of theft investigation.
A variety of product marking approaches have been employed in the industry. For example, paper tags or labels carrying bar codes may be applied to components in the course of their assembly. For many applications, such tags or labels will be lost or destroyed. Ink or paint spraying of codes such as dot matrix codes have been employed for many manufacturing processes. Where the production environment is too rigorous, however, or subsequent painting steps are involved, such an approach would be found to be unacceptable.
The provision of a permanent or traceable marking upon hard surfaces such as metal traditionally has been achieved with marking punches utilizing dies which carry a collection of fully formed characters. These "full face dies" may be positioned in a wheel or ball form of die carrier which is manipulated to define a necessarily short message as it is dynamically struck into the material to be marked. As is apparent, the necessarily complex materials involved are prone to failure and full face dies exhibit rapid wear. Generally, the legibility and abrasion resistance of the resultant marks can be considered to be only fair in quality. Additionally, the marking punch approach is considered a poor performer in marking such surfaces as epoxy coatings and the like.
Laser activated marking systems have been employed. However, such systems are of relatively higher cost and the abrasion resistance and "readability after painting" characteristics of laser formed characters are considered somewhat poor.
In 1985, U.S. Pat. No. 4,506,999 by Robertson, entitled "Program Controlled Pin Matrix Embossing Apparatus" described and claimed a computer driven dot matrix marking technique which had been successfully introduced into the marketplace. This marking approach employs a series of tool steel punches which are uniquely driven using a pneumatic floating pin impact concept to generate man readable and/or machine readable dot characters or codes. Marketed under the trade designation "PINSTAMP", these devices carry the noted steel punches or "pins" in a head assembly which is moved relative to the workpiece being marked in selected skew angles to indent a dot or pixel defining permanent message or code into a surface. The approach enjoys the advantage of providing characters of good legibility as well as permanence. Additionally, a capability for forming the message or codes during forward or reverse head movements is realized. This approach permits marking upon such surfaces as epoxy coatings. Use of the basic dot matrix character stamping device is limited, however, to piece parts which are both accessible and of adequate size.
Robertson, et al., in U.S. Pat. No. 4,808,018, entitled "Marking Apparatus with Matrix Defining Locus of Movement", issued Feb. 28, 1989, describes a dot matrix character impact marking apparatus which is capable of forming messages or arrays of characters within a very confined region. With this device, a linear array of marker pins is moved by a carriage in a manner defining an undulating locus of movement. This locus traces the matrix within which character fonts are formed by the marker pin. The carriage and head containing the marker pin are pivotally driven by a cam to provide vertical movement and by a Geneva mechanism to provide horizontal movement. Pixel positions for the matrices are physically established in concert with pin or carriage locations by a timing disk and control over the pins is generated in conjunction with an interrupt/processor approach. Each marking pin within the head assembly of this portable device is capable of marking more than one complete character for a given traverse of the head between its limits of moment.
Robertson, et al., in U.S. Pat. No. 5,015,106, issued May 14, 1991, and entitled "Marking Apparatus with Multiple Line Capability" describes a dot matrix character impact marking apparatus which achieves a multiple line capability wherein a carriage component carrying one or more marker pin cartridges moves within a singular plane locus of movement. This multiple line capability advantageously has permitted a broad variety of line configurations, for example in widely spaced positions at a workpiece. The device further employed a retrace method in generating a locus of marking movement somewhat similar to the formation of a raster in conjunction with television systems. A modular approach for the device was provided utilizing a forward housing carrying the locus defining component of the device which was then actuated from a rearwardly disposed motor containing housing component which served to drive cam assemblies at the forward portion. The carriage component of the device carried a manifold which, in turn, carried one or more marker pin cartridges, the pins of which were driven from an externally disposed valved and pressurized air supply. As before, the device performed in conjunction with a predetermined character defining matrix of pixel positions, each position of the matrix being identified to the system by a timing disk physically maneuvered with the drive components.
The success of the above products has led to further calls on the part of industry for even more compact marking systems of lower weight and higher rates of marking speed. Further, interest has developed in providing a broad range of marking capabilities for the type devices at hand. In this regard, it has been deemed desirable to achieve a matrix form of character marking utilizing a single plane undulatory motion of the pin cartridge carrying carriage, as well as providing a capability for the above-described raster form of locus of movement. This flexibility should be achievable through the utilization of software changes as opposed to the insertion of hardware-based timing components and the like. Further, it is desirable that the instruments providing for such marking be both alterable and repairable by field based personnel. A still further call has been made on the part of industry for such devices to retain the capability for full form character formation. This requires the actuation of the marker pins in a manner wherein discrete dots or pixels are not observable, the indentations formed by these pins being so closely nested as to evoke the image of a continuous line forming each character. As is apparent, A need has existed for marker pin based systems exhibiting enhanced levels of marking flexibility and compactness.